This invention is directed to an apparatus for spray coating or encapsulating discrete particles or particulate objects while the particles or objects are suspended in a gaseous fluid such as air. The discrete particles or particulate objects to be spray coated or encapsulated may be particles or objects of nutrients, therapeutic substances, seeds, fertilizers, pesticides, herbicides, rodenticides and the like. The coating or encapsulation materials serve to protect, preserve and enhance appearance or possibly engender special properties such as rumen-stable coatings releasable post-ruminatingly as feed supplements for ruminant animals.
In the processes involving encapsulation, the core material must be contained or "encapsulated" in some manner and then may be released upon demand. The processes in the art may use free-flowing solids and film-forming polymers having a release mechanism that may be based upon pH changes, temperatures, solubility, mechanical forces, light or permeability of the film.
Products, which are inherently tacky or are not normally free-flowing, can be encapsulated so as to obtain free-flowing discrete particles.
Low melting solids, waxes and liquids can be solubilized, dispersed or otherwise incorporated into a polymer matrix and then applied onto any suitable core material. Low vapor pressure liquids, although not directly capable of being encapsulated, can be encapsulated by absorbing them first onto a porous particle before encapsulating.
In the field of agriculture, seeds have been encapsulated for specific applications involving moisture and temperature conditions and to alter physical characteristics without affecting germination and growth. Insecticides, fungicides, herbicides and innoculants have been incorporated into encapsulation formulations. More acceptable rodenticides have been developed through encapsulation techniques. The release of pesticides can be controlled by use of resin films as the encapsulating material. Slow release insecticide fungicide systems have been developed that place the insecticide or fungicide on the seed and protect the plant for longer periods of time.
In the food processing industry, encapsulation can be used to provide stability during processing or to release an active ingredient, such as flavor, leavening agent, or acidulant, at a particular point in the process. Packaging can be simplified in some instances where an incompatible ingredient is encapsulated and packaged with the balance of the mixture. Oily materials may be encapsulated by absorbing them onto a suitable base before coating or by including them as part of a coating being applied. Partial coatings can be effective anti-caking treatment and may also serve as a means to apply colors, surfactants, essential oils and trace additives with a high degree of uniformity. Solid particles may be coated to retain a desired texture, greatly retard either hydration or dehydration, improve handling characteristics of both powders and larger particles, or possibly simply to improve the appearance of a product. Taste-masking ingredients, which add offensive flavor, or the stabilization of desirable flavor, have been used either by direct encapsulation or by inclusion in the coating matrix.
In the pharmaceutical field, encapsulation processes are used for purposes of stability, masking of taste and odor, timed release and for enteric properties. For instance, in the use of film-forming materials, a low melting semi-crystalline lipophilic compound may be first coated onto a particle which has a high affinity for the compound, such as a polyethylene glycol wax. Then these particles are encapsulated with a hydrophilic film that has a low affinity for the compound. The substrate and encapsulating ingredients thus work together to protect the compound from its environment.
Examples of coatings that have been used in the art include methyl and ethyl methacrylates, cellulose acetate phthalate, carboxymethyl and ethyl cellulose, polyethylene, polyvinyl acetate, polyvinylidene chloride, polyvinyl alcohol, polystyrene, cellulose propionate morpholinobutyrate, polymers of vinylpyridine and derivatives of vinylpyridine, copolymers, mixtures of polymers with other polymers and/or pigments, fillers, plasticizers, etc., beeswax, carnauba, castor wax, paraffin, corn syrups, dextrins, molasses, fats, gelatins, glycerides, glycols, gums, lecithin, stearates, sucrose, proteins, shellac, starches, and a host of others that could be mentioned.